Japanese Patent Laying-Open Nos. 7-240212 (PTD 1) and 2004-199911 (PTD 2) each describe a hybrid power supply system in which a plurality of power supplies are combined to supply power to a load using a power converter connected across the plurality of power supplies and the load. PTD 1 describes that, in the hybrid power supply device in which a fuel cell and a secondary battery are combined, properties of overall efficiency of the system with respect to a fuel cell output are previously calculated, and the output of the fuel cell is instructed to charge the secondary battery such that a range where system overall efficiency is high is selected depending on the remaining power of the secondary battery.
PTD 2 describes that, in a fuel cell system having a secondary battery, control for increasing efficiency in a specific control mode in which a fuel cell is disconnected from a hybrid power supply system is achieved by connecting the secondary battery and a load without a switching operation in the control mode.
Japanese Patent Laying-Open No. 2012-70514 (PTD 3) describes a configuration of a power converter capable of, by means of control of a plurality of switching elements, switching between an operation mode of carrying out DC/DC conversion with two DC power supplies connected in series (series connection mode) and an operation mode of carrying out DC/DC conversion with two DC power supplies used in parallel (parallel connection mode).